We are now over two years into the incredible mission of the James Webb Space Telescope (JWST). From its historic launch on December 25, 2021, to its dynamic deployment and current ongoing mission to push the boundaries of imagination, JWST has captivated the entire world with its breathtaking photos and unveiling of the cosmos' secrets. What are some of the discoveries it has made? Let’s delve into just a small sample of the discoveries that JWST has uncovered.
Exoplanet K2-18 b
While its primary mission is to look at galaxies more ancient than the Milky Way itself, JWST is also designed to look at the atmosphere of extrasolar planets and look for signs of “biosignatures”. Biosignatures are basically chemicals that, at least here on Earth, can only be produced by life. To do this, one key technique JWST will utilize is the transit method, where it observes the slight dimming of a star's light as an exoplanet passes in front of it. By carefully analyzing this dimming, JWST can discern the chemical makeup of the exoplanet's atmosphere.
This method allows JWST to detect the presence of specific gasses, such as water vapor, methane, and carbon dioxide, which are indicative of potential biosignatures. By scrutinizing the spectral signatures produced during these transits, JWST is providing valuable insights into the diverse atmospheres of exoplanets, shedding light on their formation, evolution, and potential for hosting life beyond our solar system..
One extrasolar planet that has piqued astronomer’s interest is K2-18b. K2-18 is a star system located some 124 light years away from the solar system. K2-18b is a planet orbiting that star, with a mass about eight times that of the Earth and a diameter roughly twice that of it. The possible detection of water vapor by the Hubble telescope has suggested that this planet could be a weird “hycean” planet - a planet with a dense hydrogen atmosphere, like that of Neptune and Uranus, but with a water surface.
JWST, however, has yet to confirm this finding. Instead, Webb has found evidence that carbon dioxide and methane may exist in the atmosphere of K2-18b, both of which are potential biosignatures. Additionally, more telling is the possibility that K2-18b has the possible signature of dimethyl sulfide (DMS), a molecule that is produced exclusively by life here on Earth. K2-18b might potentially be the strongest evidence we have yet that life exists outside of Earth. JWST will perform further observations to confirm these observations.
The Oldest Galaxy or First Dark Star?
NIRCam, or Near-InfraRed Camera, is a vital instrument on the James Webb Space Telescope. Its primary functions include capturing images across the near-infrared spectrum and aiding in the alignment of the telescope's 18-section mirrors. Infrared cameras are needed because the earliest galaxies are redshifted into the infrared spectrum using a process known as spectroscopy. During its first round of surveys, JWST’s NIRCam detected a galaxy with a “lookback” time of 13.4 billion years, meaning that this galaxy came into existence shortly after the Big Bang and represents the universe at its very earliest stages. However, is this truly a galaxy at all?
Some astronomers believe that this could be a “dark star”, a type of star during the first phase of stellar evolution that is created by dark matter rather than through nuclear fusion. This is because the origin of light appears as a “point” like a star in the sky, rather than as a fuzzy disk as seen with galaxies. Dark stars are hypothetical stars mainly made of regular matter like our Sun, but with a twist: they're heavily influenced by a type of mysterious substance called neutralino dark matter. Dark stars would also collapse into black holes at the end of their lives, and this may provide an explanation for the high density of ancient supermassive black holes observed in the universe.
Dark stars could be vast, stretching from 1 to 960 times the distance between the Earth and the Sun and potentially growing to millions of times the mass of our Sun before running out of dark matter fuel. If any of these dark stars somehow exist today, they might emit unique signals like gamma rays, neutrinos, and antimatter, making them detectable alongside clouds of cold hydrogen gas, which usually wouldn't contain such energetic particles. However, these types of objects, due to their immense luminosity, would be visible from this distance from the Earth and are more likely to exist at this time of the early universe.
Image credit: NASA, ESA, CSA, and STScI, M. Zamani (ESA/Webb), L. Hustak (STScI). Science: B. Robertson (UCSC), S. Tacchella (Cambridge), E. Curtis-Lake (Hertfordshire), S. Carniani (Scuola Normale Superiore), and the JADES Collaboration
Affirming Hubble Tension
It has long been known that the universe is expanding. Edwin Hubble showed this by observing galaxies through his telescope and creating the “Hubble constant,” the rate of expansion of the universe. Exactly what it’s expanding into, or why it is expanding, is not exactly known. The favored theory is that dark energy is driving the expansion of space. Hubble Space Telescope (HST), named after Edwin Hubble, has been measuring the expansion of the universe and adjusting the corresponding Hubble constant with observations.
Hubble’s constant is best described by an equation v = H_0 * D, where D represents distance and v represents velocity. If any two of these values are known, then the other can be found through simple algebraic division. However, trying to assign distance with the Hubble constant has proven challenging. In space, certain distance ladders exist that can tell us precisely how far away objects are. The best-known example of this is Cepheid variables, which is an extraordinarily precise distance ladder. When Hubble has tried to measure the distance to galaxies with the Hubble constant, and compare it to that of Cepheid variables, Hubble has shown that there is evidently a mismatch in distances.
However, instead of showing that these measurement errors are because of observational errors with Hubble, JWST has actually affirmed the Hubble tension by showing that a) Hubble’s current value for the Hubble constant is accurate and b) using its larger aperture to observe more distant Cepheid variables shows the same problem. What does this mean exactly? Astronomers aren’t exactly sure. Further observations are needed from JWST to understand the Hubble tension’s applications to cosmology.
Super Old Black Holes
Black holes aren’t all that black. In fact, the material of gas and dust surrounding a black hole, also known as an “accretion disk” can be quite bright. As matter falls toward a supermassive black hole, it forms a swirling disk called an accretion disk. This disk consists of gas, dust, and other material being drawn into the black hole due to its immense gravitational pull. As material in the accretion disk spirals inward, it rubs against other material and generates immense frictional heat. This heat causes the material to emit intense radiation across the electromagnetic spectrum, from radio waves to X-rays, as well as releasing a tremendous amount of energy, powering the brightness of quasars. Quasars are the most luminous objects known in the universe.
But here’s the catch—JWST can see quasars that existed a mere ~1 billion years after the Big Bang. How did supermassive black holes form so early in the universe’s history? By looking at data from a sample of six quasars, astronomers have found that supermassive black holes might have formed before the first galaxies, the opposite of our understanding of galactic formation. But how? We don’t know!
It’s possible that some of these “seed” black holes could have formed from the universe’s very first colossal stars. However, some of the black holes JWST is observing would have required a mass far, far greater. It’s possible that they could have formed as a result of gas clouds at the beginning of the universe, the same ones that birthed the first stars. But how the mechanics of this could have worked is simply unknown.
Click to Enlarge Image
Image credit: NASA, ESA, CSA, J. Matthee (ISTA), R. Mackenzie (ETH Zurich), D. Kashino (National Observatory of Japan), S. Lilly (ETH Zurich)
Understanding our place in space
A big selling point to the general public for JWST was the pictures it would bring. Hubble, while a research station, also served as an amazing public affairs platform. The pictures that have come from JWST have been nothing short of staggering and awe-inspiring. Pictures have come down from JWST that have put into perspective our place in the cosmos in such a way that we’ve never seen before. While not exactly scientific, these perspectives are no less important.
We’re a small planet in a massive universe. It’s unfathomable to us to think of the distances between the Earth and other stars, let alone other galaxies. With JWST, we’ve seen galaxies at the beginning of time itself, extrasolar planets both incredibly similar and different from our own, and absolutely beautiful mosaics of the Eagle Nebula’s pillars of creation and other famous nebulae. But Webb also represents a technical marvel - our ability to construct something so precise and complex to be able to see these things.
Think about it: JWST is a telescope with six times the aperture of Hubble, needed to unfold in an incredibly complex dance orchestrated from the ground, has the ability to operate at -450F below zero, equipped with multiple cameras able to see in different wavelengths of infrared light, and was packed into a rocket and shot into space a million miles away from Earth. That’s remarkable, and it’s remarkable that we humans are able to do such things despite our place in the universe.
Additionally, this was an international project. It wasn’t just humans from one country doing this for national pride - it was an international effort between multiple countries led by NASA, the European Space Agency, and the Canadian Space Agency to truly understand our place in space. Fourteen countries contributed to the telescope. JWST is truly a scientific mission, representing a profound scientific endeavor solely aimed at unraveling the mysteries of the universe, including the evolution of galaxies and the characteristics of distant solar systems. JWST serves as a symbol of the human species' dedication to exploration and discovery and shows our willingness to undertake ambitious projects for all humankind.
Image credit: NASA, ESA, CSA, STScI; J. DePasquale, A. Koekemoer, A. Pagan (STScI).
The James Webb Space Telescope stands as a testament to humanity's insatiable curiosity and relentless pursuit of knowledge. Since its historic launch, JWST has revolutionized our understanding of the cosmos, unveiling mysteries that were once beyond reach. From probing the atmospheres of distant exoplanets for signs of life to peering back in time to witness the universe's earliest moments, JWST has showcased the power of innovation and collaboration on a global scale. Moreover, JWST's profound impact extends beyond the realm of science, serving as a symbol of unity among nations and a reminder of what can be achieved when we come together to explore the wonders of the universe. As JWST continues its journey of exploration, it not only expands the frontiers of human knowledge but also inspires us to dream bigger and reach farther than ever before.
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